I don't think you're going to find too many Zesto oven owners here. You might post this question over at PMQ, where you might find someone who owns one of these ovens.
If you can post specs of the oven you're looking at, specifically BTUs, internal dimensions and stone material/thickness, along with specifications on the pizzas you make (thickness factor, size, formula, volume during peak times) then I can give you an idea of how they'll recover.
Are you trying to match the results from the Marsals with a Zesto or improve up them? What Marsals are you working with?